1. Field of the Invention
The present invention relates to a switching system including a telephone switch capable of accommodating a public switched network line or a leased line and a LAN (Local Area Network) line, and a radio communication terminal accessible by radio in such a switching system to or from a public switched network line or a leased line, and a radio communication terminal adapter for allowing such a radio communication terminal to be accommodated in a telephone switch included in such a system.
2. Description of the Background Art
Conventionally, mobile terminals, such as a cellular phone or PHS (Personal Handyphone System) terminal for use in a public switched network, use in communication a base station included in a public switched network even while staying in the premises of a general LAN system. Therefore, for instance, a call directed to a cellular phone set carried by a person, even when staying in a building or similar local premises, should be routed through a public switched network.
It is a common practice with a telephone switch to include a trunk unit connected to a public switched network and a line unit accommodating an extension network or a LAN system. PHS terminal shave functions available for a public switched network and a LAN or an extension network and selectable by the operation of a user of the terminals. A telephone switch applied to a private PHS system can accommodate both of the extension and public switched networks. PHS terminals applicable to such a private PHS system are required to be allotted to telephone numbers for both an extension and a public switched network. More specifically, when communication is to be held on such a PHS terminal via the public switched network, the telephone switch uses a telephone number A assigned for the public switched network to establish a central office call connection, whereas for communication to be held on the PHS terminal via the extension network, the telephone switch uses another telephone number B assigned for the extension network to establish an extension call connection.
Today, it is often the case that one and the same person possesses plural kinds of communications terminals, such as a cellular phone set, a PHS terminal available in a public switched network and a private branch exchange network, a conventional telephone set and an IP (Internet Protocol) phone terminal accommodated by a telephone switch in a LAN system and a personal computer or similar data processing terminal, such as a personal data assistant. In such a case, another person, intending to call the above-stated person, has to select one of the different numbers each assigned to his or her particular communication terminal.
More specifically, the conventional switching system requires a person, when originating a call to the above-stated person, to selectively use telephone numbers assigned for a public switched network or a central office line and for an extension network or an extension available to that called person. This brought about a problem that, even with a LAN system including a stabler and less expensive extension network, a person who wishes to originate a call directed to a cellular phone terminal on the extension could not use the extension network because the cellular phone terminal is adapted to communicable only with a base station of the public switched network. Particularly, with a private PHS system in which both of the extension network and the public switched network or central office lines are available to one and the same PHS terminal, a person, when originating a call meant to that PHS terminal on the extension, must appropriately select an extension number or a central office line number allotted to that terminal.
In light of the above, Japanese patent laid-open publication No. 2003-046645, for example, discloses a system in which the number of a cellular phone set is stored and which provides its base station or switching system with the function of transferring a call to be terminated on the cellular phone set to an extension network. More specifically, in the prior art system, a call originating through a public switched network to that cellular phone is transferred and terminated to its extension telephone number. That requires both a base station and a telephone switch to set a call transfer therein. In this sense, the system should preferably be provided with a simpler configuration.
Moreover, the system configured to terminate an incoming call directed to a cellular phone set onto its extension line number, as taught in the above laid-open publication, temporarily disables the functions of the cellular phone set and therefore prevents them from being effectively used.